1. The Field of the Invention
The present invention relates to a reclinable chair. In particular, although not exclusively, the invention relates to a synchro-tilt type chair in which the seat portion tilts rearwardly in synchronism with reclining action of the back portion. The invention is described primarily in the context of commercial office chairs. However, the invention is not limited in its application to commercial office chairs and may have application to any other type of seating such as public seating for theatres, aircraft or domestic seating.
2. The Relevant Technology
Reclining office chairs are well known. There are certain disadvantages associated with the conventional form of reclining office chair. One of the disadvantages is that as the occupant of the chair reclines rearwardly, his head drops in height. Therefore, the eye level of the chair""s occupant will not be maintained constant. This may pose a difficulty if the occupant is working at a computer terminal where it is desirable to maintain a constant eye level relative to the screen. Additionally, in meetings it is also desirable to maintain a constant eye level relative to the other attendees of the meeting. Any person who undergoes a dip in eye level may effectively drop out of the conversation.
Another difficulty with conventional reclining chairs is that relative movement between the back portion and the seat portion may lead to frictional grabbing of occupant""s shirt, thereby pulling out the occupant""s shirt from his trousers.
U.S. Pat. No. 5,871,258 is in respect of a reclining office chair. The seat portion of the chair has a front portion connected to a rear portion by a resilient section in order that the rear portion carries most of the occupant""s weight. The seat portion is operably connected to the reclining mechanism such that as the back portion reclines, the rear portion of the seat also tilts but additionally moves in a downward and forward motion. It will be appreciated that this further only serves to exacerbate the problem of tipping eye level. In this case, not only is the occupant""s head dropping on account of their reclining action but also, the rear portion of the seat supporting the occupant""s weight is also moving downwardly, with the practically certain result that the eye level of the occupant will dip during reclining action.
U.S. Pat. No. 5,314,237 raises the vertical height of the seat support during recline and thereby claims to achieve consistent vertical eye level. However, the chair disclosed in this US patent suffers from another shortcoming. As the seat portion lifts, the forward edge of the seat portion will accordingly be raised and thereby act as a hard edge bearing against the back of the occupant""s knees. This can lead to circulatory problems for the occupant and/or lifting of the users feet from the floor with consequent poor posture.
Flexing of seat backs in the lumbar region of the user is also a desirable feature of modern office chairs. Chair occupants come in a wide range of different sizes and weights and it is therefore necessary for chair manufacturers to produce a chair which caters for a wide range of occupant sizes and weights. A larger, weightier person will be able to flex a chair back easily. On the otherhand, a person of light build may only be able to flex the back portion with a high degree of force. Accordingly, a person of light build may not receive much satisfaction from the feature of a flexible back portion.
Another common feature of reclinable chairs is the use of recline springs to resist rearward recline. Adjustment mechanisms are often provided to adjust the spring tension of the recline springs to suit the build of the occupant of the chair. Where such adjustment mechanism operate directly against the action of the spring, e.g., by way of a rotatable knob, generally a large number of turns of the knob are required in order to gradually stiffen the spring. Otherwise, the knob would be too stiff to turn in order to bring about the required adjustment.
It is therefore an object of the present invention to provide a chair which overcomes or at least addresses some of the foregoing disadvantages.
In accordance with a first aspect of the present invention there is provided a chair including: a supporting frame; a seat portion which is foldable about a transverse fold to define a rearward portion behind the transverse fold and a forward portion, forward of the transverse fold, the seat portion being supported above the supporting frame by its rearward portion; a reclinable back portion; and a recline mechanism with which the back portion is connected for reclining action of the back portion, the recline mechanism being operably linked to the rearward portion of the seat portion such that on reclining action of the back portion, the rearward portion is moved to increase in rearward tilt angle and to obtain a net increase in height above the supporting frame, with a consequent folding of the seat portion about the transverse fold line under the weight of the occupant.
In order to achieve a foldable seat portion, the seat portion may be flexible. The seat portion may be constructed of a flexible material such as plastic. In a preferred form of the invention, the seat portion may comprise a panel which has apertures, e.g., slots to enhance its flexibility. The slotted pattern may extend across the entirety of the panel with a specific arrangement of slots provided to increase comfort for the seat occupant. For example, the slotted panel may have the slots arranged to accommodate the ischial protuberosities of the occupant. Alternatively, the slotted pattern may simply exist in a specific zone to provide flexing about the transverse fold. The transverse fold may be shaped as a straight line, depending upon the arrangement of the slots or apertures in the seat panel or according to the manner in which the seat portion is supported. The transverse fold may alternatively take the shape of a curve lying in the plane of the seat portion.
Where the seat portion takes the form of a panel, stiffening webs may be provided which offer little resistance to flexing towards the forward edge of the seat portion and greater resistance to flexing towards the rear of the seat portion. The resistance offered may progressively increase from the front edge of the seat portion towards the rear. Accordingly, the stiffening webs may be tapered to offer the varying resistance.
In an alternative less preferred form of the invention, the seat portion may comprise the forward portion and the rearward portion being articulated.
In a preferred form of the invention, the rearward portion of the seat portion is supported, at least in part, by the recline mechanism while the forward portion is unsupported. The depth position of the seat portion may be adjustable relative to the back portion and/or the supporting base. Accordingly, the positioning of the transverse fold may be variable as a function of the seat depth position. For example, the seat portion may be moveable forward/backward relative to guides forming part of the recline mechanism with the forward edge of the guides or a transition in curvature defining the transverse fold. The ease of folding may be dependent upon the depth position of the seat portion. As described above, this may be achieved by the seat portion having an increased resistance to folding in the directly rearwardly from the forward edge of the seat portion.
The recline mechanism preferably interconnects the seat portion, the supporting frame and the back portion. In a most preferred form, the recline mechanism is in the form of a four bar linkage. The four bar linkage may be replicated on each side of the chair. Therefore, the following description of the four elements of the four bar linkage may apply to single elements or alternatively to duplicated elements on opposite sides of the chair. The first linkage is in the form of a main support. The main support may be selectively height adjustable by the user. However, the main support is in normally fixed disposition relative to the supporting frame. In the most preferred form of the invention, the main support is supported at the top of a height adjustable gas spring extending upwardly as part of the supporting frame.
The second linkage of the four bar linkage may be the seat portion itself. Where the seat portion is depth adjustable, then the second linkage may comprise a guide for the depth adjustment.
The third linkage of the four bar linkage preferably comprises a front support linkage extending between the main support and the second linkage.
The fourth linkage is preferably in the form of a drive linkage which is pivotable about a drive axis through the main support, being connected to the second linkage and being operably linked to be driven about the drive axis by rearward recline action of the back portion.
Preferably, the back portion is also supported from the main support. The back portion is preferably attached to a back attach portion which is pivotally connected to the main support at a recline axis. The recline axis of the back portion is preferably below the seat portion. In a most preferred form of the invention, the recline axis is below the ischial protuberosities of the occupant.
Preferably, the back portion is biased against reclining action by a recline biasing device. This may be in the form of a one or more springs. In a most preferred form of the invention, the biasing force is adjustable. In a preferred embodiment of the invention there may be two back extension arms extending from the back portion. These extension arms could be an integral part of the back attach portion or alternatively could be rigidly connected thereto. With the two extension arms pivotally connecting the back portion to the main support, the one or more springs are preferably held by one or both of the back extension arms, with the spring(s) acting against the main support.
Preferably there are two springs in the form of leaf springs. Preferably, the first spring has a predetermined spring rate (or spring constant). The second spring may be clamped against the first spring with the combination having a resultant spring rate with the degree of clamping being variable to adjust the resultant spring rate. Preferably, the second spring has a high spring constant in its unclamped state in order that only a small clamping adjustment is required to bring about an appreciable change in the resultant spring rate of the combination.
One or more recline abutment surfaces may define the recline limit of the back portion. Preferably, the recline abutment surfaces are provided on one or both of the back extension arms and the main support.
Furthermore, there may be provided one or more forward abutment surfaces which define the forward position of the back portion. Preferably, the forward abutment surfaces are disposed on one or both of the back extension arms and the main support. In a most preferred form of the invention, one or both of the back extension arms include a pin which travels within a slot of the main support. The slot has a base which engages against the pin when the pin reaches a position of travel within the slots corresponding to the forward position of the back portion. Additionally, cushioning may be provided to cushion the abutment between the forward abutment surfaces. This may comprise an O-ring encircling the pin.
Desirably, the invention also includes a recline lock, to lock the back portion against reclining action. The recline lock may be selectively lockable by the user. In a preferred form of the invention, the recline lock acts against a lock abutment surface on one or both of the back extension arms. Preferably, the recline lock is in the form of a push rod/bar which, when selectively operated by the user acts against the lock abutment surfaces of both extension arms at the same time.
Another preferred feature of the invention is that the back portion is flexible or at least flexible at a part corresponding to the lumbar region of the occupant. Preferably the flexibility, i.e., the stiffness is adjustable. The flexibility may be adjustable selectively, although it is preferred that the adjustment takes place automatically in response to the weight imparted by the occupant on the seat portion. Preferably, the larger the weight, the greater the stiffness imparted to the back portion.
Preferably, the adjustment can be achieved through the use of a tensionable biasing device provided to act against the flexible back portion, with a varying degree of tension to impart a varying degree of stiffness to the back portion. For example, the biasing device may be in the form of a spring. Preferably, there are two flat springs lying against the back portion at a lower region thereof adjacent the connection of the back portion to the back attach portion.
Preferably, the tensioning of the biasing device is achieved by means of an interconnecting linkage which in response to the occupant""s weight on the seat portion, tensions the biasing device by a corresponding amount. Preferably, the interconnecting linkage interconnects the biasing device with the drive linkage. In a most preferred form of the invention, where the biasing device is in the form of a leaf spring lying against the back portion, the leaf spring is connected to a spring carrier forming part of the interconnecting linkage, the spring carrier being pivotally mounted to the back attached portion in a manner whereby the weight of the occupant on the seat portion is transferred through to the spring carrier so as to bend the leaf spring against the back portion. As there may be two four bar linkages provided on opposite sides of the chair, there may accordingly be provided two interconnecting linkages with two spring carriers receiving two leaf springs, The back portion may include a back frame which, in its lower regions defines a rearwardly facing channel. Preferably, each leaf spring engages within the channel on a respective side of the back frame. Preferably, each interconnecting linkage also includes two push links, each interconnecting the associated spring carrier with the associated drive linkage. The back attach portion may be in the form of a housing, i.e., the back attach housing. The spring carrier(s) and the push link(s) may be at least partly received within the back attach housing. Each leaf spring and associated spring carrier may be of integral construction.
The supporting frame may be of any type. Preferably, the supporting frame is of the conventional type with a central support and a plurality of radiating legs with castors. The supporting frame may incorporate a height adjustable gas spring.
A tension limit may be provided to prevent over-tensioning of the tensionable biasing device. For example, rotation of the spring carrier may be stopped against the back attach housing.
In accordance with a second aspect of the present invention there is provided a chair having: a supporting frame; a seat portion supported above the supporting frame; and a back portion having a flexible portion, wherein the flexibility of the flexible portion is adjustable as a function of the weight of an occupant on the seat portion.
The seat portion and the back portion could be integral or alternatively could be discrete portions of the chair. Preferably, a recline mechanism is provided which interconnects the seat portion, the back portion and the supporting base.
The flexibility of the flexible portion may be adjustable by way of a stiffness adjustment device. This may be in the form of a tensionable biasing device. The tensionable biasing device preferably acts against the flexible portion to impart stiffness thereto with the tension of the biasing device being adjustable as a function of the weight of an occupant on the seat portion. The tensionable biasing device may be interconnected by a means of an interconnection with the seat portion, the seat portion being moveable on the application of weight from an occupant whereby the weight of the occupant acts through the interconnection to adjust the biasing device as a function of the weight of the occupant. Preferably, the interconnection comprises a series of links to transfer the weight of the occupant into increased tension of the biasing device. Preferably, the biasing device is in the form of one or more springs such as leaf springs and the interconnecting linkage acts to bend the one or more springs against the flexible portion of the back, thereby increasing the stiffness of the flexible portion.
In a most preferred form of the invention, the interconnection includes a four bar synchro-tilt mechanism which tilts the seat portion synchronously with back recline. The four bar synchro-tilt mechanism may take the form of the four bar linkage described above in accordance with the first aspect of the present invention. The drive link of the four bar linkage may be connected to a push link which is in turn connected to a spring carrier as described above in accordance with the first aspect of the invention.
A tension limit may be provided to prevent over-tensioning of the tensionable biasing device. This may be in the form of a physical stop which acts against the spring carrier.
In accordance with a third aspect of the present invention there is provided a chair having: a supporting frame; a main support supported by the supporting frame; a seat portion supported above the supporting frame; a reclinable back portion operably connected with the main support for reclining action relative to the main support; a first recline spring operably connected between the main support and the reclinable back portion for resisting reclining action of the back portion; and a second recline spring operably connected between the main support and the reclinable back portion; the second recline spring being selectively adjustable to impart a varying amount of resistance to the reclining action of the back portion.
The resistance imparted by the second spring may be adjustable between a nil amount and a predetermined amount.
The first recline spring may be in the form of a leaf spring or spring bar. The second recline spring may also be in the form of a leaf spring or spring bar. The leaf springs may be flat or bent. Preferably, the first leaf spring is substantially flat when untensioned, although desirably the first leaf spring is pretensioned into a curved configuration in order to provide an initial resistance to reclining action. A forward limit may be provided to define the forward active position of the back portion. The first recline spring and selectively the second recline springs bias the back portion into the forward active position. Additionally, a rearward recline limit may also be provided to define the rearmost position of the back portion.
In one form of the invention, the adjustment device brings about adjustment of the length of the second leaf spring. Alternatively, the adjustment device may bring about adjustment of the curvature of the second leaf spring. This may be achieved by way of a cam having a cam surface bearing against the second spring, the position of the cam being moveable to adjust the curvature of the second spring. Preferably, the cam is pivotable about a pivot axis with the cam surface including a plurality of distinct portions of progressively increasing distance from the pivot axis in either a clockwise or anticlockwise direction. The cam surface may also include a stop to limit rotation of a cam about the pivot axis.
The first and second springs may be spaced from each other and may operate independently of each other. However, in a most preferred form of the invention, the first and second springs lie against each other for at least a portion of the length of the springs. In this form of the invention, the cam may be incorporated into a clamp to clamp the second recline spring against the first recline spring.
The main support may be in the form of a transversely extending main transom. Furthermore, the back portion may include two spaced arms pivotally mounted to the main transom. In this form of the invention, preferably the first leaf spring extends between the two spaced arms and bears against the side of the main support to bias the back portion against reclining action. The ends of the first leaf spring may be received in aligned, facing slots in each arm. Preferably, the second spring is shorter than the first spring with one end being received in one of the slots.
In addition to the action of the first and optionally second recline springs, the back portion may be operably connected to the seat portion whereby the weight of the occupant resists reclining action of the back portion. This may be achieved by way of a four-bar linkage supporting the seat portion with the back portion being operably connected to the four-bar linkage so that reclining action of the back portion brings about a net increase in height of the seat portion.
In accordance a fourth aspect of the present invention there is provided a chair having: a supporting frame; a main support supported by the supporting frame; a seat portion supported above the supporting frame; a reclinable back portion operably connected with the main support for reclining action relative to the main support; a first recline spring comprising an elongate spring portion having dimensions of length, width and thickness wherein the width is greater than the thickness and further having a longitudinal axis aligned with the length of the elongate spring portion, the recline spring being operably connected between the main support and the reclinable back portion for resisting reclining action of the back portion through bending about an axis transverse to the longitudinal axis, wherein the first recline spring is rotatable about the longitudinal axis to adopt any one of a plurality of spring positions, at each of which the spring portion exhibits a differing spring rate in resistance to bending about the transverse axis.
The back portion may be reclinable between a forward active position and a rear most position. For this purpose, a forward limit may be provided to define the forward active position and a rearward recline limit may also define the rear most position. In recline action, the main support and the back portion move relative to each other. The first recline spring may be arranged such that as the main support and the back portion move relative to each other, they bear against the first recline spring, tending to flex the elongate spring portion about the transverse axis thereby biasing the back portion toward the forward active position through the inherent resistance of the spring. However, at the forward active position, the arrangement may be such that the main support and the back portion exert no pretension on the first recline spring. This enables the first recline spring to be easily rotated about the longitudinal axis.
In a preferred form of the invention, an intermediate portion of the first recline spring bears against the main support with an end portion of the first recline spring bearing against the back portion. In a more preferred form of the invention, the ends of the first recline spring bear against the back portion with a central part of the first recline spring bearing against the main support. More specifically, the main support may be in the form of a transversely extending main transom. Furthermore, the back may include two spaced arms pivotally mounted to the main transom. In this form of the invention, the first recline spring may extend alongside the main transom with the two ends journaled in each arm and with a central part of the first recline spring bearing against the main transom. However, the invention is not limited to such an arrangement. It is conceivable that in an alternative arrangement the two ends of the first recline spring could be rotatably journaled in the main support with an intermediate part bearing against the back portion.
Preferably, the elongate spring portion of the first recline spring is in the form of a flat bar which may be rotated about its longitudinal axis. It will be appreciated that the flat bar can be rotated into a number of positions. There may be three positions, the first with the width dimension of the flat bar arranged to be substantially aligned with the transverse bending axis. This exhibits an easy resistance to bending. In a second adoptable spring position, the flat bar may be arranged with its width dimension diagonally to the transverse bending axis. This exhibits a medium resistance to bending. In a third adoptable position, the width of the flat bar is arranged transverse to the bending axis. With the whole of the width resisting bending, this correlates to the hardest spring position.
The spring portion is not limited to being in the form of a flat bar and other cross-sections are possible including elliptical or oval cross-sections. There may be more than one elongate spring portion incorporated into the first recline spring.
Where the first recline spring bears against the back portion and the main support, cylindrical bosses may be incorporated into the first recline spring. For example, the ends of the first recline spring may be fitted with cylindrical bosses to be journaled in the arms of the back portion. Similarly, a cylindrical boss may also be provided at an intermediate portion of the first recline spring where the first recline spring bears against the main support. In this connection, the main support may also incorporate a bearer against which the cylindrical boss bears. This may be in the form of a complementary bore or recess. In particular, the main support may have a rearward extension which incorporates a semi-cylindrical recess to accommodate the central cylindrical boss of the first recline spring.
The first recline spring may be integrally formed with the spring portion(s) and the cylindrical boss(es). However, most preferably the bosses slide onto the spring portion.
Furthermore, the invention may include an actuator to selectively rotate the recline spring. The actuator may be in the form of a paddle
Advantageously, locators are also provided to define each of the plurality of adoptable spring positions. The spring positions may be defined by complementary projections and detents provided in one or more of the cylindrical bosses and the corresponding bearer. For example, grooves may be provided in the central cylindrical boss with a rib provided in the bearer, the engagement between the rib and each one of the grooves defining each of the adoptable spring positions.
The invention may also provide a second recline spring. The second recline spring may be adjusted as with the first recline spring and accordingly may include all of the features described above in connection with the first recline spring. However, in a most preferred form of the invention the second recline spring is non-adjustable. Preferably, the arrangement is such that the second recline spring has a pre-load in the forward active position. The second recline spring may be already bent or flexed to achieve the pre-load. The second recline spring may extend alongside the first recline spring. The second recline spring may be journaled in a similar fashion as described above for the first recline spring. The second recline spring may be in the form of flat bar. However, in a preferred form of the invention, the second recline spring is in the form of a rod, preferably a cylindrical rod.
In addition to the action of the first and optional second recline springs, the back portion may be operably connected to the seat portion whereby the weight of the occupant resists reclining action of the back portion. This may be achieved by way of a four-bar linkage supporting the seat portion with the back portion being operably connected to the four-bar linkage so that reclining action of the back portion brings about a net increase in height of the seat portion.
This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.
The invention consists in the foregoing and also envisages constructions of which the following gives examples.